Differential renal function is crucial in determining which kidney to select for donor nephrectomy, often with preference given to the less functional kidney after considering anatomical and clinical factors. This study evaluates whether this approach impacts short- and long-term post-donation renal function when the more functional kidney is donated.

124 consecutive donors (mean age 49 ±12 years, 42% male) underwent donor nephrectomy at our institution from 2015 to 2022 (88% left kidney donations). Preoperative Dimercaptosuccinic acid (DMSA) scans, pre- and post-operative creatinine levels were collected. Renal function post-donation was evaluated using CKD-EPI eGFR at 6 months, 1, 3, and 5 years. DMSA scans determined differential renal function preoperatively, and donors of less functional kidneys (Group 1, n =72, 47.74 ±2.00%) were compared to those donating more functional kidneys (Group 2, 52.26 ±2.00%). Post-donation eGFR loss was analysed using Pearson's correlation and Student's t-tests.

Baseline characteristics were similar: age (49 ±13 vs 49 ±11 years), gender (43% vs 40% male), BMI (24.2 ±3.8 vs 24.4 ±2.9), preoperative GFR (99.4 ±18.7 vs 98.6 ±19.2), and laterality of kidney donation (Left: 86% vs 92%). Post-donation percentage eGFR loss at 6 months (32.6 ±12.6% vs 31.2 ±16.6%), 1 year (31.9 ±9.5% vs 29.7 ±16.9%), 3 years (30.8 ±12.5% vs 23.7 ±20.7%), and 5 years (29.9 ±10.0% vs 25.3 ±29.7%) did not differ significantly between groups (p>0.05). Preoperative remnant kidney function for both groups (as determined by the product of DMSA% of remnant kidney) did not correlate with post-donation eGFR (r =0.046 to 0.207).

Despite larger eGFR declines in those donating the more functional kidney, the difference was not statistically significant. DMSA-assessed remnant kidney function also showed no correlation with long-term eGFR decline. Therefore, differential renal function should not be the sole criterion for choosing the donor kidney. Decisions should incorporate anatomical considerations, surgeon experience, and patient-specific factors. Other considerations in determining the side for kidney donation include vascular anatomy, renal conditions (such as cysts or stones), and the surgeon's experience and preference.